1. Field of the Invention
The present invention relates to a light receiver which reproduces and outputs a light clock signal synchronized with the light signal data row inputted by using a light saturable absorber, and the light data row.
2. Description of the Related Art
FIG. 11 is a light digital reproduction apparatus shown on B-12-21, 1999, by Ohtani (KDD) et al. in a great spring meeting of xe2x80x9cThe Institute of Electronics, Information and Communication Engineers (IEICE)xe2x80x9d, and the saturable absorption characteristic of the electric field absorption type light modulator (hereinafter, written as EA modulator, EA is an abbreviation for Electro-Absorption) is utilized. When the light input signal and the light clock pulse generated by the light pulse generator are inputted into the light saturable absorber, because the absorption saturation occurs when the input signal has the sufficient intensity corresponding to the characteristic of the light saturable absorber, the light pulse generated by the light pulse generator passes when the input light signal is xe2x80x9c1xe2x80x9d, and when the input light signal is xe2x80x9c0xe2x80x9d, it is absorbed and coding occurs. At this time, it is necessary that the light clock pulse which is the reproduced output light source, is in timed relationship with the input signal pulse in the optimum phase condition in the saturable absorber in which coding is conducted. In the conventional example, the clock electric signal in timed relationship with the repeated frequency of the input light signal data row is extracted from the light absorption current taken out from the electrode of the EA modulator which is the saturable absorber, and by the electric clock signal, the light modulator is driven, and the light clock pulse in timed relationship with the light input signal is generated.
In the coding of the light signal by the light signal using the light saturable absorber, it is necessary that the synchronization of both the light signals in the light saturable absorber is established, and the optimum phase relationship is always kept for them. In this case, as in the conventional example, when the process in which the synchronization clock electric signal is extracted once from the clock signal, and the clock electric signal is electrically/light converted, is passed through, because it is difficult that the phase variation in the clock signal path is intrinsically compensated for, and the same high speed operation as the light signal speed is required for the electric circuit, there is a problem that cost becomes high.
A light receiver according to the first invention has: a light clock pulse generation light source to control the repeated frequency of a light clock pulse by the input current or input voltage; a wave-branching means for wave-branching the light from the clock pulse generation light source into the first light and the second light, each having a wavelength xcex2; an output means for outputting the first light wave-branched by the wave-branching means to the output terminal of the light clock; a wave-composing means for wave-composing the second light wave-branched by the wave-branching means with the signal light, which has a wavelength xcex1, inputted from the input terminal; a light saturable absorber which absorbs the light wave-composed by the wave-composing means and outputs the photo current, and in which a light absorption coefficient is decreased corresponding to the light input level; an optical filter which separates the light with wavelength xcex1 and the light with wavelength xcex2, which are outputted from the light saturable absorber; a dither signal source for modulating the phase of the light pulse generated from the clock pulse generation light source by the dither signal; and a phase controller for controlling so that the phase of the light source generated by the light clock pulse generation light source and the phase of the signal light inputted from the input terminal are in timed relationship with 0xc2x0, according to the output of the light saturable absorber which generates the photo current, and the output of the dither signal source.
A light receiver corresponding to the second invention, which comprising: a light clock pulse generation light source to control the repeated frequency of a light clock pulse by the input current or input voltage; a wave-branching means for wave-branching the light from the clock pulse generation light source into the first light (wavelength xcex2) and the second light (wavelength xcex2); an output means for outputting the first light wave-branched by the wave-branching means to the output terminal of the light clock; a wave-composing means for wave-composing the second light wave-branched by the wave-branching means with the signal light (wavelength xcex1) inputted from the input terminal; a light saturable absorber whose light absorption coefficient is decreased corresponding to the light input level of the wave-composed light signal; an optical filter which separates the light of wavelength xcex1 and the light or wavelength xcex2 outputted from the light saturable absorber; a light receiving unit to electrically convert the separated light by the optical filter; a dither signal source for modulating the phase of the light pulse generated from the clock pulse generation light source by the dither signal; and a phase controller for controlling so that the phase of the light source generated by the light clock pulse generation light source and the phase of the signal light inputted from the input terminal are in timed relationship with 0xc2x0, according to the output of the light saturable absorber which generates the photo current, and the output of the dither signal source.
The light receiver according to the third invention, has a light variable delay unit to control a delay amount by the input current or the input voltage, and a dither signal source to modulate the light input signal by the dither signal.
The light receiver according to the fourth invention, has a light variable delay unit to control a delay amount by the input current or the input voltage, and a dither signal source to modulate the light input signal by the dither signal.
The light receiver according to the fifth invention has: the first light circulator which outputs the inputted light signal to the light saturable absorber, and outputs the light pulse reproduced in the light saturable absorber; the second light circulator to terminate the light signal outputted from the light saturable absorber, and output the light clock pulse to the light saturable absorber; a light clock pulse generation light source to control the repeated frequency of a light clock pulse by the input current or input voltage; a wave-branching means for wave-branching the light from the clock pulse generation light source into the first light and the second light; an output means for outputting the first light clock wave-branched by the wave-branching means to the output terminal; a reproduction means for outputting the second light clock wave-branched by the wave-branching means from the second light circulator to the light saturable absorber, wherein the light saturable absorber outputs the reproduced light signal through the first light circulator; and a phase controller for controlling so that the phase of the light source generated by the light clock pulse generation light source is in timed relationship with the phase of the signal light inputted from the input terminal, according to the output of the light saturable absorber to generate the photo current and the output of the dither signal source.
The light receiver according to the sixth invention has: the first light circulator to output the inputted signal light to the light saturable absorber; the second light circulator to terminate the light signal outputted from the light saturable absorber; a light clock pulse generation light source to control the repeated frequency of a light clock pulse by the input current or input voltage; a wave-branching means for wave-branching the light from the light clock pulse generation light source into the first light and the second light; an output means for outputting the first light wave-branched by the wave-branching means to the output terminal of the light clock; a light saturable absorber to output the second light clock wave-branched by the wave-branching means to the first light circulator; a light receiving unit to wave-branch the light signal from the first light circulator and to electrically convert it; and a phase controller for controlling so that the phase of the light source generated by the light clock pulse generation light source is in timed relationship with the phase of the signal light inputted from the input terminal, according to the output of the light receiving unit and the output of the dither signal source.
The light receiver according to the seventh invention has: a light variable delay unit to control a delay amount by the input current or the input voltage; and a dither signal source to modulate the phase of the light input signal by the dither signal.
The light receiver according to the eighth invention has: a light variable delay unit to control a delay amount by the input current or the input voltage; and a dither signal source to modulate the light input signal by the phase of the dither signal.
In the light receiver according to the ninth invention, the repeated frequency of the light clock pulse generation light source is 1/n (n is a natural number) of the input light signal bit rate.